1. Field of the Invention
The present invention relates, in general, to plugs for use in pipe systems and, in particular, to a pneumatic plug for use in pipe systems, in which the plug has a pressure release valve.
2. Information Disclosure Statement
Drain, waste, and vent (“DWV”) pipe or plumbing systems often include access openings or ports that allow the interior of the pipes of the pipe system to be inspected and/or cleaned. Likewise, sewer systems often include sewer pipes that empty into manholes or catch basins through openings or ports in the manhole or catch basin chambers. Access opening configurations for such pipe systems can vary in size and shape, although many configurations are standardized. In one common configuration, an access opening (often referred to as a “clean-out”) is provided at the end of a relatively short section of cylindrical pipe that extends away from the axis of the main pipe section. Clean-outs may extend from a main pipe section at any angle. Those that extend approximately 90 degrees from the main pipe section are commonly called “clean-out tees” (referring to the T-shape created by the intersecting pipe sections). Other access openings include, but are not limited to, roof vents, storm drains, closet bends, and pipe ends, and the sewer pipe openings or ports in a manhole or catch basin chamber.
Access openings may also be used to test the integrity of the pipe system. Such a test is conducted by placing temporary plugs into all openings of the DWV system to create a closed system, and then pressurizing the now-closed system with a fluid, such as water or air, for a period of time to determine if the DWV system is leak free, in which case it will hold a rated pressure for the test duration. After successful testing, the plugs are removed. Such temporary plugs can generally be categorized into mechanical plugs and pneumatic plugs. Existing mechanical plugs typically include devices that seal pipe systems via mechanical activation, such as by turning a threaded connection member to expand an elastomeric ring that seals an inner surface of a pipe section. Existing pneumatic plugs include elongate elastomeric bladders that are attached directly to a source of fluid such as, typically and preferably, an air source. The bladders are inserted into the pipe system through the clean-outs or other access openings and are then inflated with the fluid so as to seal the pipe section as the bladder expands within the pipe. After testing, the temporary plugs are deflated or deactivated and then removed from the pipe system. In addition to the testing of DWV systems and/or sewer systems, it is often desired to seal a pipe line during a maintenance function, in which flow through the pipe is blocked for maintenance purposes even though pressure testing of the pipe system is not being performed.
Although some existing pneumatic plugs may display a maximum inflation pressure on the outside of the bladder, this does not provide protection for overinflation, but instead relies on the diligence of the operator and the existence and accuracy of an air inlet pressure gauge. If the elastomeric bladders of such pneumatic plugs become overinflated, problems could occur. The result when over-inflation occurs can be damage to the plug, damage to the pipe, inconvenience and delay of the testing process, or injury to the user if the plug explodes due to over-inflation. Known prior art solutions to this problem involve using an external pressure regulator or external pressure release device on the air inlet, but these solutions are cumbersome and are often ignored by operators, or the operator may be careless when using such regulators or pressure release valves. Pressure regulators do work but increase the inflation time, and they must be accurately set prior to use. Furthermore, each different type of pneumatic plug typically requires a different pressure setting to be made by the operator to accommodate plugs for different pipe diameters. External pressure release valves are also known to work, but are subject to failure if they become plugged and are typically unreliable for making accurate pressure settings. Such external pressure release valves must also be attached between the plug and the inflation hose, are often bulky, and also slow down the inflation process.
Some existing pneumatic plugs include integrated pressure release devices. However, such prior art pressure release devices tend to leak, do not provide repeatable results, and may disrupt testing of the pipe system. Specifically, some pneumatic plugs include release valves that have mechanical springs and seals, and have been found to be prone to fouling and often tend to collect contamination. Other pneumatic plugs include release valves that are positioned on the backside of the elastomeric bladder, venting into the pipe system being tested, and tend to expel the plug out of the pipe system and clean-out access, thereby disrupting the testing process.
One example of such a prior art plug is that made by Cherne Industries, Inc., Minneapolis, Minn., U.S.A., and sold under the trademark LONG TEST-BALL. This pneumatic plug has the disadvantage of having mechanical parts including springs and seals that tend to leak or not accurately release pressure at a repeatably accurate value.
Another pneumatic plug is made by GT Water Products, Inc., Moorpark, Calif., U.S.A., and sold under the trademark SAFE-T-SEAL, and has a pressure release on the bottom of the plug, remote from the pressurizing inlet and venting into the pipe system, which can cause the plug to be forced out of the pipe as the relieved pressure expels into the sealed pipe system being tested.
Still another prior art pneumatic plug is that disclosed in U.S. Pat. No. 7,597,118 (issued Oct. 9, 2009), fully included herein by reference, in which a portion of the elastomeric bladder is elastically deflected to unblock a pressure release channel when the bladder becomes overinflated.
As a result, there is a need for an improved pneumatic plug for use with a pipe section having a generally cylindrical internal pipe wall. The pneumatic plug should be easy to use and should not require the operator to make additional settings or readings. It should be reliable, provide repeatable results, and it should not require additional external equipment or otherwise disrupt testing of the pipe system.
It is therefore desirable to have a pneumatic plug for use in pressure testing a pipe system, in which the plug includes a pressure release valve in its inflation end remote from the pressurized pipe system being tested, wherein the pressure release valve provides a repeatable chosen release pressure, and in which the pressure release valve is more reliable than prior art pneumatic plug pressure release valves.